alleryStart learning →What is the electric potential 1.0 m from a point charge of Q = -25 nC?
A+2.2 x 10^2 V
B-2.2 x 10^4 V
C-2.2 x 10^-2 V
D-2.2 x 10^2 V
Answer & Solution
Correct answer: D. -2.2 x 10^2 V
1. V = kQ/r = (8.99 x 10^9 N m^2/C^2)(-25 x 10^-9 C) / (1.0 m).
2. This works out to -224.75 V, which rounds to -2.2 x 10^2 V.
3. Because the source charge Q is negative, the potential itself is negative, unlike the always-positive electric field magnitude.
4. Option A keeps the same size but drops the sign, forgetting that potential carries the sign of its source charge directly, unlike field magnitude.
_Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section 18.4 Electric Potential_
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